Journal
SCIENCE OF THE TOTAL ENVIRONMENT
Volume 373, Issue 2-3, Pages 534-541Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.scitotenv.2006.12.021
Keywords
phosphorus; aluminum; sequential extraction; lake sediment; lake chemistry
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Phosphorus (P) is the limiting macronutrient for primary production in most lakes. Seasonal anoxia in the hypolimnion of lakes has been strongly correlated with internal P loading to the water column. Gravimetric sediment cores were collected before and after the onset of anoxia in six Maine (USA) lakes during the summer of 2003. This study investigates the relative importance of P sequestration by aluminum hydroxide (Al(OH)(3(s))), and ferric (oxy)hydroxide (Fe(OH)(3(S))) dissolution with subsequent P release in lakes with varying trophic status. Two lakes, Pennesseewassee and Highland, are oligotrophic. The remaining lakes, China, Cobbosseecontee, Webber and Salmon, have varying levels of productivity. Sediment P, Al and Fe in the top 10 cm were extracted sequentially using ammonium chloride (NH4Cl), bicarbonate-dithionite (BD), and sodium hydroxide (NaOH) at 25 degrees C. The results suggest that a sediment [NH4Cl - Al + BD - Al + NaOH25-Al]:[NH4Cl - Fe + BD - Fe] molarratio > 3 and a sediment [NaOH25-Al]:[NH4Cl - P + BD-P] molar ratio > 25 predict low P flux from sediments during the development of anoxia, as proposed by Kopacek et al. [Kopacek J, Borovec J, Hejzlar J, Ulrich K, Norton S, Amirbahman A. Aluminum control of Phosphorus Sorption in Lake Sediments. Environ Sci Technol 2005; 39: 8784-8789.], despite the development of anoxia in and the release of Fe(II) from the hypolimnia of the two study lakes. However, when these molar ratios are not exceeded the model does not adequately describe sedimentary P flux. The application of the model proposed by Kopacek et al. to Cobbosseecontee Lake suggests that its sediment may be a source of P to the water column. However, water column data indicate little to no sedimentary P flux. Therefore, the lack of P flux may be attributed to the absence of Fe (III) reduction in the Cobbosseecontee Lake sediment or perhaps to the slow diagenesis of organically-bound P. (c) 2006 Elsevier B.V. All rights reserved.
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